A conventional electro-photographic type image forming apparatus includes: a plurality of photosensitive drums; exposure units each configured to expose each surface of each photosensitive drum to light to form an electrostatic latent image on each surface; developing units each configured to form a toner image on the surface of each photosensitive drum; and a belt unit on which toner images on the photosensitive drums are transferred.
United States Patent Application Publication No. 2013/328325 discloses such image forming apparatus including: a plurality of process units each being provided with a photosensitive drum; a belt unit positioned above the process units; LED units each facing a corresponding photosensitive drum from below; and a pair of first frames each formed with a plurality of drum positioning grooves and disposed interposing the belt unit in a leftward/rightward direction.
Each photosensitive drum has a pair of flange members each configured to be abutted on the drum positioning groove of the corresponding first frame from below by moving the photosensitive drum upward. By this abutment, positioning of the photosensitive drum relative to the belt unit is achieved.